Transmission of feedback information for multi-carrier operation

ABSTRACT

Techniques for sending feedback information for multi-carrier operation are described. In an aspect, feedback information may be sent on an uplink carrier that may or may not be paired with a downlink carrier on which data transmission is sent. A user equipment (UE) may receive data transmission on a downlink carrier among a plurality of downlink carriers. The UE may determine feedback information for the data transmission, determine an uplink carrier to use to send the feedback information from among a plurality of uplink carriers, and send the feedback information on the uplink carrier. In another aspect, feedback information for multiple downlink carriers may be sent on at least one uplink carrier using Single-Carrier Frequency Division Multiple Access (SC-FDMA). A UE may receive data transmissions on a plurality of downlink carriers, determine feedback information for the data transmissions, and send the feedback information on at least one uplink carrier using SC-FDMA.

The present application claims priority to provisional U.S. ApplicationSer. No. 61/175,382, entitled “UPLINK HYBRID AUTOMATIC REPEAT REQUEST(HARM) FEEDBACK IN MULTICARRIER OPERATION,” filed May 4, 2009, assignedto the assignee hereof and incorporated herein by reference.

BACKGROUND

I. Field

The present disclosure relates generally to communication, and morespecifically to techniques for sending feedback information in awireless communication system.

II. Background

Wireless communication systems are widely deployed to provide variouscommunication content such as voice, video, packet data, messaging,broadcast, etc. These wireless systems may be multiple-access systemscapable of supporting multiple users by sharing the available systemresources. Examples of such multiple-access systems include CodeDivision Multiple Access (CDMA) systems, Time Division Multiple Access(TDMA) systems, Frequency Division Multiple Access (FDMA) systems,Orthogonal FDMA (OFDMA) systems, and Single-Carrier FDMA (SC-FDMA)systems.

A wireless system may include a number of base stations that can supportcommunication for a number of user equipments (UEs). A UE maycommunicate with a base station via the downlink and uplink. Thedownlink (or forward link) refers to the communication link from thebase station to the UE, and the uplink (or reverse link) refers to thecommunication link from the UE to the base station.

A wireless system may support operation on multiple carriers. A carriermay refer to a range of frequencies used for communication and may beassociated with certain characteristics. For example, a carrier maycarry synchronization signals, or may be associated with systeminformation describing operation on the carrier, etc. A carrier may alsobe referred to as a channel, a frequency channel, etc. A base stationmay send data on one or more carriers on the downlink to a UE. The UEmay send feedback information on the uplink to support data transmissionon the downlink. It may be desirable to efficiently send the feedbackinformation on the uplink.

SUMMARY

Techniques for sending feedback information in a wireless communicationsystem supporting multiple carriers on the downlink (or downlinkcarriers) and one or more carriers on the uplink (or uplink carriers)are described herein. In an aspect, feedback information may be sent onan uplink carrier that may or may not be paired with a downlink carrieron which data transmission is sent. In one design, a UE may receive datatransmission on a downlink carrier among a plurality of downlinkcarriers. The UE may determine feedback information for the datatransmission. The feedback information may comprise acknowledgement(ACK) information, channel quality indicator (CQI) information, and/orsome other information. The UE may determine an uplink carrier to use tosend the feedback information from among a plurality of uplink carriers.The UE may then send the feedback information on the uplink carrier.

In another aspect, feedback information for multiple downlink carriersmay be sent on at least one uplink carrier using SC-FDMA. In one design,a UE may receive data transmissions on a plurality of downlink carriersand may determine feedback information (e.g., ACK information, CQIinformation, etc.) for the data transmissions. The UE may send thefeedback information on at least one uplink carrier using SC-FDMA. TheUE may send the feedback information with SC-FDMA in various manners, asdescribed below.

A base station may perform complementary processing to recover thefeedback information sent by the UE. Various aspects and features of thedisclosure are described in further detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 shows an exemplary transmission structure.

FIG. 3 shows a structure for sending ACK information.

FIG. 4A shows one-to-one feedback mapping.

FIG. 4B shows many-to-one feedback mapping.

FIG. 4C shows another many-to-one feedback mapping.

FIG. 5 shows transmission of feedback information with relaxed SC-FDMA.

FIG. 6 shows transmission of feedback information with strict SC-FDMA.

FIG. 7 shows a process for sending feedback information.

FIG. 8 shows an apparatus for sending feedback information.

FIG. 9 shows a process for receiving feedback information.

FIG. 10 shows an apparatus for receiving feedback information.

FIG. 11 shows another process for sending feedback information.

FIG. 12 shows another apparatus for sending feedback information.

FIG. 13 shows another process for receiving feedback information.

FIG. 14 shows another apparatus for receiving feedback information.

FIG. 15 shows a block diagram of a base station and a UE.

DETAILED DESCRIPTION

The techniques described herein may be used for various wirelesscommunication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and othersystems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA system may implement a radiotechnology such as Global System for Mobile Communications (GSM). AnOFDMA system may implement a radio technology such as Evolved UTRA(E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are part ofUniversal Mobile Telecommunication System (UMTS). 3GPP Long TermEvolution (LTE) and LTE-Advanced (LTE-A) are new releases of UMTS thatuse E-UTRA, which employs OFDMA on the downlink and SC-FDMA on theuplink. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the systems and radiotechnologies mentioned above as well as other systems and radiotechnologies. For clarity, certain aspects of the techniques aredescribed below for LTE, and LTE terminology is used in much of thedescription below.

FIG. 1 shows a wireless communication system 100, which may be an LTEsystem or some other system. System 100 may include a number of evolvedNode Bs (eNBs) 110 and other network entities. An eNB may be an entitythat communicates with the UEs and may also be referred to as a Node B,a base station, an access point, etc. UEs 120 may be dispersedthroughout the system, and each UE may be stationary or mobile. A UE mayalso be referred to as a mobile station, a terminal, an access terminal,a subscriber unit, a station, etc. A UE may be a cellular phone, apersonal digital assistant (PDA), a wireless modem, a wirelesscommunication device, a handheld device, a laptop computer, a cordlessphone, a wireless local loop (WLL) station, a smart phone, a netbook, asmartbook, etc.

The system may support hybrid automatic retransmission (HARQ) in orderto improve reliability of data transmission. For HARQ, a transmitter maysend a transmission of a transport block (or packet) and may send one ormore additional transmissions, if needed, until the transport block isdecoded correctly by a receiver, or the maximum number of transmissionshas been sent, or some other termination condition is encountered. Aftereach transmission of the transport block, the receiver may send anacknowledgement (ACK) if the transport block is decoded correctly or anegative acknowledgement (NACK) if the transport block is decoded inerror. The transmitter may send another transmission of the transportblock if a NACK is received and may terminate transmission of thetransport block if an ACK is received. ACK information may comprise ACKand/or NACK and may also be referred to as HARQ feedback.

FIG. 2 shows an exemplary transmission structure 200 that may be usedfor the downlink and uplink. The transmission timeline for each link maybe partitioned into units of subframes. A subframe may have apredetermined duration, e.g., one millisecond (ms), and may bepartitioned into two slots. Each slot may include six symbol periods foran extended cyclic prefix or seven symbol periods for a normal cyclicprefix.

LTE utilizes orthogonal frequency division multiplexing (OFDM) on thedownlink and single-carrier frequency division multiplexing (SC-FDM) onthe uplink. OFDM and SC-FDM partition a frequency range into multiple(N_(FFT)) orthogonal subcarriers, which are also commonly referred to astones, bins, etc. Each subcarrier may be modulated with data. Ingeneral, modulation symbols are sent in the frequency domain with OFDMand in the time domain with SC-FDM. The spacing between adjacentsubcarriers may be fixed, and the total number of subcarriers (N_(FFT))may be dependent on the system bandwidth. For example, N_(FFT) may beequal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5,5, 10 or 20 MHz, respectively.

For each of the downlink and uplink, multiple resource blocks may bedefined in each slot with the N_(FFT) total subcarriers. Each resourceblock may cover K subcarriers (e.g., K=12 subcarriers) in one slot. Thenumber of resource blocks in each slot may be dependent on the systembandwidth and may range from 6 to 110. On the uplink, the availableresource blocks may be divided into a data section and a controlsection. The control section may be formed at the two edges of thesystem bandwidth (as shown in FIG. 2) and may have a configurable size.The data section may include all resource blocks not included in thecontrol section. The design in FIG. 2 results in the data sectionincluding contiguous subcarriers.

A UE may be assigned resource blocks in the control section to sendcontrol information to an eNB. The UE may also be assigned resourceblocks in the data section to send data and possibly control informationto the eNB. The control information may comprise feedback information,scheduling request, etc. The feedback information may comprise ACKinformation, CQI information, etc. The UE may send data and/or controlinformation at any given moment. Furthermore, the UE may send ACKinformation, CQI information, and/or other control information at anygiven moment. The UE may send only data or both data and controlinformation on a Physical Uplink Shared Channel (PUSCH) on resourceblocks in the data section. The UE may send only control information ona Physical Uplink Control Channel (PUCCH) on resource blocks in thecontrol section. Different types of control information may be combinedand sent together in order to maintain a single-carrier waveform. Forexample, ACK information may be sent alone on ACK resources, or with CQIinformation on CQI resources.

A number of PUCCH formats may be supported, e.g., as shown in Table 1.PUCCH formats 1a and 1b may be used to send one or two bits (e.g., ofACK information) in a single modulation symbol. PUCCH format 2 may beused to send 20 bits (e.g., of CQI or ACK information) in 10 modulationsymbols. PUCCH formats 2a and 2b may be used to send 21 or 22 bits(e.g., of both ACK and CQI information) in 11 modulation symbols.

TABLE 1 PUCCH Formats PUCCH Modulation Number of Number of ModulationFormat Scheme Bits/Subframe Symbols/Subframe 1a BPSK 1 1 1b QPSK 2 1 2QPSK 20 10 2a QPSK + BPSK 21 11 2b QPSK + QPSK 22 11

FIG. 3 shows a structure 300 for sending ACK information on the PUCCHfor a case in which each slot includes seven symbol periods. For ACKstructure 300, a resource block includes four symbol periods for ACKinformation and three symbol periods for a reference signal. In the leftslot, ACK information may be sent in symbol periods 0, 1, 5 and 6, and areference signal may be sent in symbol periods 2, 3 and 4. In the rightslot, ACK information may be sent in symbol periods 7, 8, 12 and 13, anda reference signal may be sent in symbol periods 9, 10 and 11. ACKinformation and reference signal may also be sent in other manners on apair of resource blocks.

A UE may process ACK information as follows. The UE may map one or twobits of ACK information to a modulation symbol d(0) based on BPSK orQPSK. The UE may then modulate and spread a reference signal sequencewith the modulation symbol, as follows:

a _(n)(k)=w(n)·d(0)·r(k), for k=0, . . . , K−1 and n=0, . . . , N−1,  Eq (1)

where r(k) is a reference signal sequence,

w(n) is an orthogonal sequence used to spread ACK information,

a_(n)(k) is the n-th data sequence for ACK information, and

N is the number of symbol periods in which ACK information is sent.

As shown in equation (1), the reference signal sequence may be modulatedwith modulation symbol d(0) to obtain a modulated sequence. Themodulated sequence may then be spread with orthogonal sequence w(n) toobtain N data sequences, where N=4 in FIG. 3. The N data sequences maybe sent in N symbol periods in each resource block, e.g., as shown inFIG. 3.

The UE may generate the reference signal for ACK information, asfollows:

q _(i)(k)=w(i)·r(k), for k=0, . . . , K−1 and i=0, . . . , L−1,   Eq (2)

where q_(i)(k) is the i-th pilot sequence for ACK information, and

L is the number of symbol periods in which the reference signal is sent.

As shown in equation (2), the reference signal sequence may be spreadwith orthogonal sequence w(i) to obtain L pilot sequences, where L=3 inFIG. 3. The L pilot sequences may be sent in L symbol periods in eachresource block, e.g., as shown in FIG. 3.

A number of reference signal sequences may be defined based on differentcyclic shifts of a base sequence. The base sequence may be a Zadoff-Chusequence, a pseudo-random sequence, etc. Up to K different referencesignal sequences may be obtained with up to K different cyclic shifts ofthe base sequence, where K is the length of the base sequence. Only asubset of the K reference signal sequences may be selected for use, andthe selected reference signal sequences may be spaced apart as much aspossible in terms of their cyclic shifts. The reference signal sequencesmay also be referred to as different cyclic shifts of the base sequence.

The system may support multi-carrier operation with multiple carriers onthe downlink and one or more carriers on the uplink. A carrier used forthe downlink may be referred to as a downlink carrier, and a carrierused for the uplink may be referred to as an uplink carrier. An eNB maysend data transmission on one or more downlink carriers to a UE. The UEmay send feedback information on one or more uplink carriers to the eNB.For clarity, much of the description below is for the case in which thefeedback information comprises HARQ feedback. Data transmission and HARQfeedback may be sent in various manners.

FIG. 4A shows a design of one-to-one HARQ feedback mapping withsymmetric downlink/uplink carrier configuration. In this design, eachdownlink (DL) carrier is paired with a corresponding uplink (UL)carrier. An eNB may send data transmission on a Physical Downlink SharedChannel (PDSCH) on a particular downlink carrier to a UE. The UE maysend HARQ feedback on a corresponding uplink carrier to the eNB.

In the example shown in FIG. 4A, the eNB may send data transmissions onthree downlink carriers 1, 2 and 3 to the UE. The eNB may also sendthree downlink grants for the data transmissions on the three downlinkcarriers, one downlink grant for the data transmission on each downlinkcarrier. Each downlink grant may include pertinent parameters (e.g.,modulation and coding scheme, resource blocks, etc.) used for datatransmission to the UE. The UE may receive and decode the datatransmission on each downlink carrier based on the downlink grant forthat data transmission and may send HARQ feedback on the correspondinguplink carrier.

For one-to-one HARQ feedback mapping, HARQ feedback for a singledownlink carrier may be sent on a single uplink carrier. A downlinkgrant may be sent on a downlink carrier used for data transmission or ona different downlink carrier. In one design, HARQ feedback may be senton an uplink carrier paired with the downlink carrier on which thedownlink grant is sent, regardless of where the data transmission issent. The uplink carrier used for HARQ feedback may then be paired withthe downlink carrier on which a downlink grant is sent. Furthermore,HARQ feedback may be sent on an ACK resource identified based ondownlink resource used to send the downlink grant, as described below.

FIG. 4B shows a design of many-to-one HARQ feedback mapping withasymmetric downlink/uplink carrier configuration. In this design, alldownlink carriers may be paired with a single uplink carrier. An eNB maysend data transmission on one or more downlink carriers to a UE. The UEmay send HARQ feedback on the uplink carrier to the eNB.

FIG. 4C shows a design of many-to-one HARQ feedback mapping withsymmetric downlink/uplink carrier configuration and cross-carriercontrol operation. Each downlink carrier may be paired with acorresponding uplink carrier. An eNB may send data transmission on aparticular downlink carrier to a UE. The UE may send HARQ feedback on anuplink carrier that may or may not be paired with the downlink carrier.

In the example shown in FIG. 4C, the eNB may send data transmissions onthree downlink carriers 1, 2 and 3 to the UE. The eNB may also sendeither three per-carrier downlink grants or a single multi-carrierdownlink grant for the data transmissions on the three downlinkcarriers. A per-carrier downlink grant may convey pertinent parametersfor data transmission on a single downlink carrier. A multi-carrierdownlink grant may convey pertinent parameters for data transmissions onmultiple downlink carriers. The UE may receive and decode the datatransmissions on all downlink carriers and may send HARQ feedback on adesignated uplink carrier.

In general, for many-to-one HARQ feedback mapping (e.g., as shown inFIGS. 4B and 4C), HARQ feedback for multiple downlink carriers may besent on a single uplink carrier. HARQ feedback for a given downlinkcarrier may be sent on an uplink carrier that may or may not be pairedwith the downlink carrier. Many-to-one HARQ feedback mapping may be usedfor (i) asymmetric downlink/uplink carrier configuration where thenumber of downlink carriers is larger than the number of uplink carriersand/or (ii) cross-carrier control operation regardless of thedownlink/uplink carrier configuration.

An eNB may send zero or more transmissions of downlink controlinformation (DCI) on each downlink carrier. Each DCI may be sent on oneor more Control Channel Elements (CCEs) for a Physical Downlink ControlChannel (PDCCH), which may be sent in the first M symbol periods of asubframe, where M may be 1, 2 or 3. Each CCE may include nine resourceelement groups (REGs), and each REG may include four resource elements.Each resource element may correspond to one subcarrier in one symbolperiod and may be used to send one modulation symbol. A DCI may carry aper-carrier downlink grant or a multi-carrier downlink grant for a UE.The UE may send HARQ feedback on ACK resources determined based on thefirst CCE used to send DCI carrying a downlink grant for the UE, asdescribed below.

In an aspect, HARQ feedback may be sent on an uplink carrier that may ormay not be paired with a downlink carrier on which data transmission issent. A scheme may be used to determine which uplink carrier to use tosend HARQ feedback for data transmission on a given downlink carrier inmulti-carrier operation.

In a first design, HARQ feedback may be sent on a designated uplinkcarrier based on many-to-one HARQ feedback mapping, e.g., as shown inFIG. 4B or 4C. The designated uplink carrier may be conveyed in variousmanners. In one design, DCI for data transmissions on multiple downlinkcarriers may be sent on a single downlink carrier, e.g., as shown inFIG. 4C. HARQ feedback for all downlink carriers may then be sent on theuplink carrier that is paired with the downlink carrier used to send theDCI. In another design, the designated uplink carrier used to send HARQfeedback may be signaled to a specific UE, e.g., via Radio ResourceControl (RRC) signaling, or DCI, or some other mechanism.

In a second design, HARQ feedback may be sent based on eitheruplink-downlink carrier pairing or a designated uplink carrier. WhichHARQ feedback mapping to use may be configurable and may be conveyed invarious manners. In one design, a flag may be used to indicate whetherto send HARQ feedback using uplink-downlink carrier pairing or adesignated uplink carrier. The flag may be set to (i) a first value(e.g., 0) to indicate that HARQ feedback should be sent on an uplinkcarrier paired with a downlink carrier or (ii) a second value (e.g., 1)to indicate that HARQ feedback should be sent on a designated uplinkcarrier.

The flag may be sent in various manners. In one design, the flag may bebroadcast in system information to all UEs. In another design, the flagmay be sent to a specific UE, e.g., via RRC signaling, or DCI, or someother mechanism. A new UE that supports the flag may send HARQ feedbackon the paired uplink carrier or the designated uplink carrier, asindicated by the flag. A legacy UE that does not support the flag maysend HARQ feedback on the paired uplink carrier.

In another aspect, HARQ feedback for multiple downlink carriers (whichmay also be referred to as multi-carrier HARQ feedback) may be sent onat least one uplink carrier using SC-FDMA. For SC-FDMA, modulationsymbols may be transformed from the time domain to the frequency domainwith a discrete Fourier transform (DFT) to obtain frequency-domainsymbols. The frequency-domain symbols may be mapped to subcarriers usedfor transmission, and zero symbols with signal value of zero may bemapped to subcarriers not used for transmission. The mapped symbols maythen be transformed from the frequency domain to the time domain with aninverse fast Fourier transform (IFFT) to obtain time-domain samples foran SC-FDMA symbol. SC-FDMA may thus be characterized by modulationsymbols being sent in the time domain and converted to the frequencydomain with DFT prior to mapping to subcarriers. SC-FDMA is differentfrom OFDM, which may be characterized by modulation symbols being sentin the frequency domain and mapped directly to subcarriers, withoutgoing through a DFT. HARQ feedback may be sent with SC-FDMA in variousmanners.

In one design, HARQ feedback for multiple downlink carriers may be senton an uplink carrier based on relaxed SC-FDMA, which may be one versionof SC-FDMA. For relaxed SC-FDMA, HARQ feedback for different downlinkcarriers may be sent on different ACK resources such that asingle-carrier waveform may not be maintained for the uplinktransmission. A single-carrier waveform may be maintained if an uplinktransmission is sent on contiguous subcarriers and if a single referencesignal sequence is used for spreading across frequency.

In a first design of relaxed SC-FDMA, different downlink carriers may bemapped to different frequency regions of an uplink carrier, onefrequency region for each downlink carrier. Each frequency region maycorrespond to a different set of one or more resource blocks. Thedifferent frequency regions may be defined by different frequencyoffsets from a reference frequency, which may be the boundary betweenthe data and control regions.

Per-carrier downlink grants may be sent for data transmissions onmultiple downlink carriers. In this case, HARQ feedback for datatransmission on each downlink carrier may be sent on ACK resourcedetermined based on the first CCE in which the corresponding per-carrierdownlink grant is sent.

A multi-carrier downlink grant may also be sent for data transmissionson multiple downlink carriers. HARQ feedback may be sent in variousmanners for this case. In one design, HARQ feedback for each downlinkcarrier may be sent on ACK resource determined based on (i) the firstCCE in which DCI carrying the multi-carrier downlink grant is sent and(ii) the downlink carrier on which data transmission is sent. Forexample, the first CCE may determine the orthogonal sequence and thereference signal sequence, and the downlink carrier on which the datatransmission is sent may determine the frequency region. In this design,the first CCE used for the DCI carrying the multi-carrier downlink grantshould not be reused as the first CCE on another downlink carrier forDCI carrying another downlink grant for another UE in order to avoidmultiple downlink grants being mapped to the same ACK resource. Inanother design, HARQ feedback for each downlink carrier may be sent onACK resource determined based on the CCEs in which the DCI carrying themulti-carrier downlink grant is sent. The DCI carrying the multi-carrierdownlink grant may be for data transmissions on Q downlink carriers,where Q is greater than one. HARQ feedback for the Q downlink carriersmay be sent on Q ACK resources corresponding to Q CCEs starting with thefirst CCE in which the DCI carrying the multi-carrier downlink grant issent. Each CCE may be mapped to different ACK resource. Q CCEs may bereserved or used to send the DCI carrying the multi-carrier downlinkgrant to ensure a sufficient number of ACK resources for multi-carrierHARQ feedback.

In a second design of relaxed SC-FDMA, a shared frequency region on anuplink carrier may be used to send HARQ feedback for multiple downlinkcarriers. Per-carrier downlink grants may be sent for data transmissionson multiple downlink carriers. HARQ feedback for data transmission oneach downlink carrier may be sent on ACK resource determined based onthe first CCE used for DCI carrying a downlink grant for the datatransmission on that downlink carrier. The first CCE used for DCI on onecarrier should not be reused as the first CCE for DCI on another carrierin order to avoid multiple downlink grants mapping to the same ACKresource. A scheduler may satisfy this restriction by sending DCIs onappropriate CCEs. Alternatively, a multi-carrier downlink grant may besent for data transmissions on multiple (Q) downlink carriers. In thiscase, Q CCEs may be reserved or used for DCI carrying the multi-carrierdownlink grant to provide Q ACK resources for HARQ feedback for the Qdownlink carriers.

FIG. 5 shows a design of sending HARQ feedback for multiple downlinkcarriers with relaxed SC-FDMA using different frequency regions of anuplink carrier. In the example shown in FIG. 5, three downlink carriersmay be used to send downlink grants and data transmissions, and oneuplink carrier may be used to send HARQ feedback. Each downlink carriermay include 12 CCEs with indices of 1 through 12. The three downlinkcarriers may thus include a total of 36 CCEs, which may be mapped to 36ACK indices.

Each CCE for each downlink carrier may be mapped to one ACK resource inthe left slot and one ACK resource in the right slot of a subframe. EachACK resource may be associated with a specific orthogonal sequencedenoted as Wx, a specific reference signal sequence denoted as CSy, anda specific resource block denoted as RBz, where x, y and z may beindices for orthogonal sequence, reference signal sequence, and resourceblock, respectively. Each ACK resource may thus be identified by a (Wx,CSy, RBz) tuple. For the example shown in FIG. 5, 12 ACK resourcesdenoted as Res1 through Res12 may be defined for a given resource blockwith four reference signal sequences CS1 through CS4 and threeorthogonal sequences W1 through W3. The four reference signal sequencesmay correspond to four different (e.g., one zero and three non-zero)cyclic shifts of the base sequence. The three orthogonal sequences maybe different Walsh sequences of length four for the case in which HARQfeedback is sent in four symbol periods, as shown in FIG. 3.

A total of 36 ACK resources may be defined with three resource blocksRB1, RB2 and RB3 in each slot. The 12 CCEs for downlink carrier 1 may bemapped to the 12 ACK resources in resource block RB1. The 12 CCEs fordownlink carrier 2 may be mapped to the 12 ACK resources in resourceblock RB2. The 12 CCEs for downlink carrier 3 may be mapped to the 12ACK resources in resource block RB3. The CCE mapped to each ACK resourceis shown in FIG. 5. For example, CCE1 for downlink carrier 1 may bemapped to ACK resource Res1 in the left slot and to ACK resource Res7 inthe right slot in resource block 1.

FIG. 5 shows a design in which the 12 CCEs for each downlink carrier areassigned indices of 1 through 12. In another design, the CCEs for alldownlink carriers mapped to the same uplink carrier may be assignedunique indices based on common CCE numbering across all of thesedownlink carriers. For example, if the three downlink carriers in FIG. 5are mapped to the same uplink carrier, then the 12 CCEs for downlinkcarrier 1 may be assigned indices 1 through 12, the 12 CCEs for downlinkcarrier 2 may be assigned indices 13 through 24, and the 12 CCEs fordownlink carrier 3 may be assigned indices 25 through 36. The use of thecommon CCE numbering may avoid collisions when HARQ feedback formultiple downlink carriers are mapped to the same uplink carrier.

In the example shown in FIG. 5, five per-carrier downlink grants aresent for data transmissions on downlink carriers 1, 2 and 3. Eachdownlink grant is sent in DCI on one or more CCEs of one downlinkcarrier. HARQ feedback for data transmission on each downlink carrier issent on ACK resource determined based on the first CCE used for the DCIcarrying the downlink grant for the data transmission.

For example, DCI carrying downlink grant 1 is sent in CCEs 2 and 3 ofdownlink carrier 1. Downlink grant 1 conveys parameters for datatransmission on downlink carrier 1. HARQ feedback for this datatransmission is sent on ACK resources mapped to CCE 2, which is thefirst CCE used for the DCI carrying downlink grant 1. In particular,HARQ feedback is sent on ACK resource Res4 in the left slot and also onACK resource Res4 in the right slot, as shown in FIG. 5. DCI carryingdownlink grant 2 is sent in CCE 5 of downlink carrier 1, and downlinkgrant 2 conveys parameters for data transmission on downlink carrier 2.HARQ feedback for this data transmission is sent on ACK resource Res2 inthe left slot and on ACK resource Res5 in the right slot, which aremapped to CCE 5 corresponding to the first CCE used for the DCI carryingdownlink grant 2. Downlink grants and HARQ feedback for other datatransmissions are shown in FIG. 5.

In another design, HARQ feedback for multiple downlink carriers may besent on an uplink carrier based on strict SC-FDMA, which may be anotherversion of SC-FDMA. For strict SC-FDMA, HARQ feedback for differentdownlink carriers may be sent such that single-carrier waveform may bemaintained for an uplink transmission.

In a first design of strict SC-FDMA, HARQ feedback for multiple downlinkcarriers may be sent with ACK bundling. An eNB may send datatransmissions on multiple downlink carriers to a UE. The UE may decodethe data transmission on each downlink carrier and may obtain an ACK orNACK for the data transmission. For ACK bundling, the ACKs and/or NACKsfor all data transmissions may be combined (e.g., with a logical ANDoperation) to obtain a single ACK or NACK, which may be referred to as abundled ACK or NACK. In particular, a bundled ACK may be generated forall data transmissions if ACKs are obtained for all data transmissions,and a bundled NACK may be generated if NACK is obtained for any datatransmission. The UE may send HARQ feedback comprising the bundled ACKor NACK on a single ACK resource. This ACK resource may be determinedbased on a specific rule, e.g., the first CCE of the lowest downlinkcarrier used for DCI carrying a downlink grant for the UE. The eNB mayresend all data transmissions if a bundled NACK is received and mayterminate all data transmissions if a bundled ACK is received.

In a second design of strict SC-FDMA, HARQ feedback for multipledownlink carriers may be sent using PUCCH format 2 shown in Table 1. ForPUCCH format 2, up to twenty bits may be sent on a pair of resourceblocks in one subframe. This may be achieved by mapping the twenty bitsto ten QPSK modulation symbols and modulating a reference signalsequence with each of the ten modulation symbols to generate ten datasequences. Five data sequences may be sent in five symbol periods of afirst resource block, and the remaining five data sequences may be sentin five symbol periods of a second resource block. Twenty bits canaccommodate a number of ACKs/NACKs for HARQ feedback.

In one design, a separate frequency region in the control section may beused to send HARQ feedback using PUCCH format 2. This separate frequencyregion may be specified by an offset from either a frequency regionnormally used for HARQ feedback or a UE-specific frequency location.This separate frequency region may be conveyed to a UE via RRC signalingor some other means. Several UEs may share the same frequency region forsending HARQ feedback using PUCCH format 2 in order to reduce overhead.These UEs would not be scheduled for data transmission on the downlinkat the same time to avoid multiple UEs using the same frequency regionfor HARQ feedback. A UE may send HARQ feedback either (i) on normal ACKresource using PUCCH format 1a or 1b or (ii) in the separate frequencyregion using PUCCH format 2, depending on the number of ACKs/NACKs tosend.

In a third design of strict SC-FDMA, HARQ feedback for multiple downlinkcarriers may be sent using PUCCH format 1b shown in Table 1. For PUCCHformat 1b, two bits may be sent on a pair of resource blocks with onereference signal sequence and one orthogonal sequence, as describedabove for FIG. 3. More than two bits may be sent in several manners.

In one design, more than two bits may be sent using PUCCH format 1b byremoving orthogonal spreading. In this design, a UE may be assigned areference signal sequence for sending HARQ feedback. The UE may send upto 16 bits of HARQ feedback by mapping these 16 bits to eight QPSKmodulation symbols, modulating the reference signal sequence with eachof the eight modulation symbols to generate eight data sequences, andsending the eight data sequences in eight symbol periods of two resourceblocks. In one design, the reference signal sequence assigned to the UEmay be determined based on (i) the first CCE in the lowest downlinkcarrier used for DCI carrying a per-carrier downlink grant for the UE or(ii) the first CCE used for DCI carrying a multi-carrier downlink grantfor the UE.

A scheduler may ensure that a reference signal sequence reserved for theUE to send HARQ feedback without orthogonal spreading is not assigned toanother UE for sending HARQ feedback in the same resource block. Thismay be achieved by sending DCI for another UE on a first CCE that doesnot map to the reserved reference signal sequence. CCEs that map to thereserved reference signal sequence may be used to send DCIs for otherUEs, but not as the first CCE. Alternatively, a CCE structure may bedefined with certain CCEs mapping to the same reference signal sequence.In this case, a multi-carrier downlink grant or multiple per-carrierdownlink grants may be sent to the UE on the CCEs, and the referencesignal sequence mapped to these CCEs may be used to send HARQ feedbackwithout orthogonal spreading.

When orthogonal spreading is removed, the reference signal sequences mayexperience undesirable correlation properties in non-flat fadingchannels. This effect may be mitigated by ensuring that the referencesignal sequence used to send HARQ feedback without orthogonal spreadinghas certain cyclic shift gaps to other reference signal sequences usedto send HARQ feedback in the same resource block.

In another design, more than two bits may be sent using PUCCH format 1bby reducing orthogonal spreading with an orthogonal sequence of lengthtwo instead of four. In this design, two UEs may be assigned the samereference signal sequence but different orthogonal sequences of lengthtwo for sending HARQ feedback. Each UE may send up to eight bits of HARQfeedback by mapping these eight bits to four QPSK modulation symbols,modulating and spreading each modulation symbol to generate two datasequences, and sending eight data sequences for the four modulationsymbols in eight symbol periods of two resource blocks. In one design,the reference signal sequence and the orthogonal sequence assigned to aUE may be determined based on (i) the first CCE in the lowest downlinkcarrier used for DCI carrying a per-carrier downlink grant for the UE or(ii) the first CCE used for DCI carrying a multi-carrier downlink grantfor the UE.

A scheduler may reserve a reference signal sequence and a shortorthogonal sequence for a UE to send HARQ feedback with reducedorthogonal spreading. This short orthogonal sequence of length two maycorrespond to two normal orthogonal sequences of length four. Thescheduler may ensure that the reference signal sequence and the twonormal orthogonal sequences reserved for the UE are not assigned toanother UE for sending HARQ feedback on the same resource block. Thismay be achieved by sending DCI for another UE on a first CCE that doesnot map to the reserved reference signal sequence and normal orthogonalsequences. CCEs that map to the reserved reference signal sequence andnormal orthogonal sequences may be used to send DCIs for other UEs, butnot as the first CCEs.

FIG. 6 shows a design of sending HARQ feedback with strict SC-FDMA. Inthe example shown in FIG. 6, three downlink carriers may be used to senddownlink grants and data transmissions, and one uplink carrier may beused to send HARQ feedback. Each downlink carrier may include 12 CCEs,and 36 total CCEs for the three downlink carriers may be mapped to 36ACK indices. Each CCE may be mapped to one ACK resource in the left slotand one ACK resource in the right slot of a subframe, as shown in FIG.6.

In the example shown in FIG. 6, UE 1 is scheduled for data transmissionson all three downlink carriers. DCI carrying downlink grant 1 for UE 1is sent in CCEs 2 and 3 of downlink carrier 1, another DCI carryingdownlink grant 2 for UE 1 is sent in CCE 5 of downlink carrier 1, andyet another DCI carrying downlink grant 3 for UE 1 is sent in CCE 8 ofdownlink carrier 1. Downlink grants 1, 2 and 3 convey parameters fordata transmissions on downlink carriers 1, 2 and 3, respectively. UE 1sends HARQ feedback for the data transmissions on the three downlinkcarriers with relaxed SC-FDMA using PUCCH format 1b and no orthogonalspreading. UE 1 is assigned reference signal sequence CS2, which ismapped to the first CCE2 used for DCI carrying downlink grant 1. UE 1sends HARQ feedback for all three downlink carriers using referencesignal sequence CS2 and no orthogonal spreading.

Reference signal sequence CS2 is used for ACK resources Res4, Res5 andRes6 that map to CCEs 2, 6 and 10 in the left slot and to CCEs 2, 5 and12 in the right slot. CCEs 5, 6, 10 and 12 may not be used as the firstCCE for DCI for another UE to avoid another UE using reference signalsequence CS2 in either slot. However, CCEs 5, 6, 10 and 12 may be usedas non-starting CCEs for DCIs. For example, another DCI may be sent inCCEs 4, 5 and 6.

In one design, a decision on whether to send HARQ feedback withoutorthogonal spreading or with reduced orthogonal spreading may bedependent on the number of ACKs/NACKs to send by a UE. For example,reduced orthogonal spreading may be used if four or fewer ACKs/NACKs areto be sent, and no orthogonal spreading may be used if more than fourACKs/NACKs are to be sent.

For both relaxed SC-FDMA and strict SC-FDMA, a number of UEs may sendHARQ feedback on the same resource block by using different referencesignal sequences and possibly different orthogonal sequences. To reduceinterference between the UEs sharing the same resource block, one ormore reference signal sequences may be removed. This may be especiallydesirable to reduce interference to a UE sending HARQ feedback withoutorthogonal spreading or with reduced orthogonal spreading.

As noted above, a UE may send both HARQ feedback and data in a givenslot. In one design, the UE may send both HARQ feedback and data on thePUSCH based on strict SC-FDMA. In another design, the UE may send dataon the PUSCH and may also send HARQ feedback on the PUCCH based onrelaxed SC-FDMA. The UE may also send HARQ feedback and data in othermanners.

In another design, HARQ feedback for multiple downlink carriers may besent on at least one uplink carrier with channel selection. A UE may beassigned multiple (S) pairs of ACK resources in a subframe, with eachpair including one ACK resource in each slot of the subframe. The Spairs of ACK resources may be associated with S CCEs used to send one ormore downlink grants for the UE (e.g., as shown in FIG. 5 or 6) or maybe determined in other manners. The UE may have B ACKs/NACKs to send fordata transmissions on multiple downlink carriers. The B ACKs/NACKs maybe for (i) B transport blocks sent on B downlink carriers, one transportblock per downlink carrier, or (ii) B transport blocks sent on B/2downlink carriers with multiple-input multiple-output (MIMO), twotransport blocks per downlink carrier, or (iii) B transport blocks senton one or more downlink carriers in other manners. For MIMO, P transportblocks may be sent simultaneously on P layers, one transport block perlayer, where P may be equal to 1, 2, etc. The P layers may be formedwith a precoding matrix applied to data by an eNB prior to transmissionof the data on the downlink.

In one design of ACK transmission with channel selection, the UE mayselect one of the S pairs of ACK resources as well as a particularsignal value to send on the selected pair of ACK resources based on theB ACKs/NACKs to send by the UE. In one design, a mapping table with2^(B) entries may be defined, one entry for each of the 2^(B) possiblecombinations of the B ACKs/NACKs. For example, a first entry in themapping table may be for a combination of B ACKs, a second entry may befor a combination of B−1 ACKs followed by a NACK, a third entry may befor a combination of B−2 ACKs, followed by a NACK, followed by an ACK,etc. Each entry of the mapping table may be associated with a specificpair of ACK resources to use (from among the S pairs of ACK resources)and a specific signal value to send on this pair of ACK resources.

Table 2 shows an exemplary mapping table for mapping B ACKs/NACKs to anACK resource and a signal value. In general, each combination ofACKs/NACKs may be mapped to any suitable combination of ACK resource andsignal value.

TABLE 2 Mapping Table ACKs/NACKs ACK Resource Signal Value ACK ACK . . .ACK ACK Resource 1 Value x ACK ACK . . . ACK NACK Resource 2 Value y ACKACK . . . NACK ACK Resource 3 Value x . . . . . . . . . . . . . . . . .. NACK NACK . . . NACK NACK Resource S Value y

As an example, ten transport blocks may be sent on five downlinkcarriers with MIMO, two transport blocks per downlink carrier. Fivepairs of ACK resources may be assigned to the UE. A mapping table with2¹⁰=1024 entries may be defined, one entry for each of the 1024 possiblecombination of the ten ACKs/NACKs. Each entry in the mapping table maybe associated with one of the five pairs of ACK resources as well as aspecific 2-bit value to send on this pair of ACK resources. The UE maysend ten ACKs/NACKs for the ten transport blocks by (i) looking up themapping table with the specific combination of ACKs/NACKs to send, (ii)determining which pair of ACK resources and which signal value to use,and (iii) sending the signal value on this pair of ACK resources.

The S pairs of ACK resources may be considered as S channels for ACKinformation. Channel selection refers to the selection of a particularpair of ACK resources or channel on which to send ACK information.Channel selection may enable transmission of more ACKs/NACKs for a givennumber of ACK resources, e.g., using only one channel. This may beachieved by mapping multiple combinations of ACKs/NACKs (which may belikely to be mutually exclusive) to the same combination of channel andsignal value. Channel selection may also avoid the use of all S channelsat the same time, which may require more transmit power and more poweramplifier (PA) back-off since a single-carrier waveform is notpreserved.

In one design, channel selection may be used with orthogonal spreading.For the design shown in FIG. 3, a single ACK/NACK or two ACKs/NACKs maybe mapped to a single modulation symbol d(0) based on BPSK or QPSK,respectively. This modulation symbol may be spread with orthogonalsequence w(i) of length four as shown in equation (2) and transmitted oneach of a pair of ACK resources. Up to four combinations of ACKs/NACKsmay be supported with one modulation symbol for ACK information sentwith orthogonal spreading.

In another design, channel selection may be used without orthogonalspreading. Up to eight modulation symbols may be sent on a pair of ACKresources by removing the orthogonal spreading, as described above. Morecombinations of ACKs/NACKs may be supported by a pair of ACK resourcesby removing the orthogonal spreading.

In yet another design, channel selection may be used with reducedorthogonal spreading. Up to four modulation symbols may be sent on apair of ACK resources by spreading with an orthogonal sequence of lengthtwo, as described above. More combinations of ACKs/NACKs may besupported by a pair of ACK resources by reducing the orthogonalspreading.

In one design, channel selection may be used without bundling, asdescribed above. In this case, the UE may generate one ACK/NACK for eachtransport block received on the downlink. In another design, channelselection may be used with bundling, which may be performed in variousmanners. In one design of bundling, the UE may bundle ACKs/NACKs for alltransport blocks sent with MIMO on each downlink carrier and may obtainone bundled ACK/NACK for each downlink carrier. In another design, theUE may bundle ACKs/NACKs for all transport blocks sent on all downlinkcarriers for each layer and may obtain one bundled ACK/NACK for eachlayer. The bundled ACKs/NACKs for all downlink carriers or layers maythen be sent with channel selection in similar manner as regularACKs/NACKs.

As shown in FIG. 3, a UE may send ACK information in two slots of asubframe. The UE may encode and send the ACK information in variousmanners. In one design, the UE may send the ACK information withrepetition across the two slots of a subframe. The UE may generate Ccode bits for the ACK information, where C≧1, send the C code bits onone resource block in the left slot, and send the same C code bits onanother resource block in the right slot. The UE may thus send the sameC code bits with repetition in the two slots of a subframe. In anotherdesign, the UE may send the ACK information with joint coding across thetwo slots of a subframe. The UE may generate 2C code bits for the ACKinformation, send the first C code bits on one resource block in theleft slot, and send the remaining C code bits on another resource blockin the right slot. The UE may send the ACK information with eitherrepetition or joint coding for each of the designs described above. TheUE may also send the ACK information in other manners.

FIG. 7 shows a design of a process 700 for sending feedback informationin a wireless communication system. Process 700 may be performed by a UE(as described below) or by some other entity. The UE may receive datatransmission on a downlink carrier among a plurality of downlinkcarriers (block 712). The UE may determine feedback information for thedata transmission (block 714). The feedback information may comprise ACKinformation (e.g., ACK and/or NACK), or CQI information, or some otherinformation, or a combination thereof. The UE may determine an uplinkcarrier to use to send the feedback information from among a pluralityof uplink carriers (block 716). The UE may then send the feedbackinformation on the uplink carrier (block 718).

The UE may determine the uplink carrier to use to send the feedbackinformation in various manners. In one design, the UE may receive a flagindicative of whether to use a designated uplink carrier or a paireduplink carrier to send the feedback information. The paired uplinkcarrier may be associated with (i) the downlink carrier used for thedata transmission, or (ii) a downlink carrier used to send a downlinkgrant, or (iii) and some other downlink carrier. The UE may determinethe uplink carrier to use to send the feedback information based on theflag. The UE may send the feedback information on the designated uplinkcarrier if the flag is set to a first value and on the paired uplinkcarrier if the flag is set to a second value.

In another design, the UE may receive signaling identifying the uplinkcarrier to use to send the feedback information. The signaling may besent specifically to the UE via upper layer (e.g., RRC) signaling or maybe broadcast to all UEs.

In yet another design, the UE may receive a downlink grant on a seconddownlink carrier among the plurality of downlink carriers. The downlinkgrant may be for the data transmission on the downlink carrier. Theuplink carrier to use to send the feedback information may be the uplinkcarrier paired with the second downlink carrier used to send thedownlink grant, which may or may not be the downlink carrier used fordata transmission.

In one design, for many-to-one mapping, feedback for data transmissionson the plurality of downlink carriers may be sent on the same uplinkcarrier. The UE may receive a second data transmission on anotherdownlink carrier among the plurality of downlink carriers. The UE maysend feedback information for the second data transmission on the sameuplink carrier.

FIG. 8 shows a design of an apparatus 800 for sending feedbackinformation in a wireless communication system. Apparatus 800 includes amodule 812 to receive data transmission on a downlink carrier among aplurality of downlink carriers, a module 814 to determine feedbackinformation for the data transmission, a module 816 to determine anuplink carrier to use to send the feedback information from among aplurality of uplink carriers, and a module 818 to send the feedbackinformation on the uplink carrier.

FIG. 9 shows a design of a process 900 for receiving feedbackinformation in a wireless communication system. Process 900 may beperformed by a base station/eNB (as described below) or by some otherentity. The base station may send data transmission on a downlinkcarrier among a plurality of downlink carriers to a UE (block 912). Thebase station may determine an uplink carrier used by the UE to sendfeedback information (e.g., ACK information, CQI information, etc.) forthe data transmission from among a plurality of uplink carriers (block914). The base station may receive the feedback information on theuplink carrier from the UE (block 916).

In one design, the base station may send a flag indicative of whether touse a designated uplink carrier or a paired uplink carrier to send thefeedback information. The uplink carrier used to send the feedbackinformation may be determined based on the flag. In another design, thebase station may send signaling identifying the uplink carrier used tosend the feedback information. In yet another design, the base stationmay send a downlink grant on a second downlink carrier among theplurality of downlink carriers. The uplink carrier used to send thefeedback information may be paired with the second downlink carrier usedto send the downlink grant. The second downlink carrier may or may notbe the downlink carrier used for data transmission.

In one design, the base station may send a second data transmission onanother downlink carrier among the plurality of downlink carriers to theUE. The base station may receive feedback information for the seconddata transmission on the same uplink carrier from the UE.

FIG. 10 shows a design of an apparatus 1000 for receiving feedbackinformation in a wireless communication system. Apparatus 1000 includesa module 1012 to send data transmission on a downlink carrier among aplurality of downlink carriers to a UE, a module 1014 to determine anuplink carrier used by the UE to send feedback information for the datatransmission from among a plurality of uplink carriers, and a module1016 to receive the feedback information on the uplink carrier from theUE.

FIG. 11 shows a design of a process 1100 for sending feedbackinformation in a wireless communication system. Process 1100 may beperformed by a UE (as described below) or by some other entity. The UEmay receive data transmissions on a plurality of downlink carriers(block 1112) and may determine feedback information for the datatransmissions (block 1114). The feedback information may comprise ACKinformation, or CQI information, or some other information, or acombination thereof The UE may send the feedback information on at leastone uplink carrier using SC-FDMA (block 1116).

In one design, the UE may send the feedback information in a pluralityof frequency regions of the at least one uplink carrier, one frequencyregion for each downlink carrier. The UE may receive signalingidentifying at least one frequency offset for the plurality of frequencyregions. In another design, the UE may send the feedback information ina single frequency region of a single uplink carrier. In yet anotherdesign, the UE may send the feedback information on a plurality ofresources for the at least one uplink carrier. The plurality ofresources may correspond to different frequency regions, or differentorthogonal sequences, or different reference signal sequences, or someother type of resources, or a combination thereof. The UE may receivesignaling identifying the plurality of resources to use to send thefeedback information. The signaling may be dedicated signaling (e.g.,RRC signaling) sent specifically to the UE or broadcast signaling (e.g.,system information) sent to all UEs.

In one design, the UE may send the feedback information with repetitioncoding. In this design, the UE may generate a plurality of code bitsbased on the feedback information. The UE may then send the plurality ofcode bits in a first slot of a subframe and also in a second slot of thesubframe. In another design, the UE may send the feedback informationwith joint coding. In this design, the UE may generate a plurality ofcode bits based on the feedback information. The UE may send a firstsubset (e.g., the first half) of the plurality of code bits in a firstslot of a subframe and may send a second subset (e.g., the second half)of the plurality of code bits in a second slot of the subframe.

In one design, the UE may send the feedback information for the datatransmissions on the plurality of downlink carriers without bundling. Inthis design, the UE may send an ACK or a NACK for the data transmissionon each downlink carrier (or for each transport block sent on eachdownlink carrier). In another design, the UE may send the feedbackinformation for the data transmissions on the plurality of downlinkcarriers with bundling. In this design, the UE may determine an ACK or aNACK for the data transmission on each downlink carrier. The UE may thendetermine a bundled ACK or NACK for the data transmissions on theplurality of downlink carriers based on the ACK or NACK for the datatransmission on each downlink carrier. The UE may send the bundled ACKor NACK in similar manner as an ACK or NACK for data transmission on asingle downlink carrier.

FIG. 12 shows a design of an apparatus 1200 for sending feedbackinformation in a wireless communication system. Apparatus 1200 includesa module 1212 to receive data transmissions on a plurality of downlinkcarriers, a module 1214 to determine feedback information for the datatransmissions, and a module 1216 to send the feedback information on atleast one uplink carrier using SC-FDMA.

FIG. 13 shows a design of a process 1300 for receiving feedbackinformation in a wireless communication system. Process 1300 may beperformed by a base station/eNB (as described below) or by some otherentity. The base station may send data transmissions on a plurality ofdownlink carriers to a UE (block 1312). The base station may receivefeedback information for the data transmissions on the plurality ofdownlink carriers from the UE (block 1314). The feedback information maybe sent by the UE on at least one uplink carrier using SC-FDMA and maycomprise ACK information, or CQI information, or some other information,or a combination thereof.

In one design, the base station may receive the feedback informationfrom a plurality of frequency regions of the at least one uplinkcarrier, one frequency region for each downlink carrier. The basestation may send signaling identifying at least one frequency offset forthe plurality of frequency regions. In another design, the base stationmay receive the feedback information from a single frequency region of asingle uplink carrier. In yet another design, the base station mayreceive the feedback information on a plurality of resources for the atleast one uplink carrier. The plurality of resources may correspond todifferent frequency regions, or different orthogonal sequences, ordifferent reference signal sequences, or a combination thereof. The basestation may send signaling identifying the plurality of resources. Thesignaling may be dedicated signaling sent specifically to the UE orbroadcast signaling sent to all UEs.

In one design, the base station may perform decoding for the feedbackinformation sent with repetition coding in two slots of a subframe. Inanother design, the base station may perform joint decoding for thefeedback information sent with joint coding across two slots of asubframe.

In one design, the base station may receive ACK information sent withoutbundling. In this design, the base station may receive an ACK or a NACKfor the data transmission on each downlink carrier (or for eachtransport block). In another design, the base station may receive ACKinformation sent with bundling. In this design, the base station mayobtain a bundled ACK or NACK for the data transmissions on the pluralityof downlink carriers. The bundled ACK or NACK may be determined by theUE based on an ACK or a NACK obtained for data transmission on eachdownlink carrier. The base station may resend all data transmissions onthe plurality of downlink carriers if a bundle NACK is obtained and mayterminate all data transmissions if a bundle ACK is obtained.

FIG. 14 shows a design of an apparatus 1400 for receiving feedbackinformation in a wireless communication system. Apparatus 1400 includesa module 1412 to send data transmissions on a plurality of downlinkcarriers to a UE, and a module 1414 to receive feedback information forthe data transmissions on the plurality of downlink carriers from theUE, the feedback information being sent by the UE on at least one uplinkcarrier using SC-FDMA.

The modules in FIGS. 8, 10, 12 and 14 may comprise processors,electronic devices, hardware devices, electronic components, logicalcircuits, memories, software codes, firmware codes, etc., or anycombination thereof.

FIG. 15 shows a block diagram of a design of a base station/eNB 110 anda UE 120, which may be one of the base stations/eNBs and one of the UEsin FIG. 1. Base station 110 may be equipped with T antennas 1534 athrough 1534 t, and UE 120 may be equipped with R antennas 1552 athrough 1552 r, where in general T≧1 and R≧1.

At base station 110, a transmit processor 1520 may receive data from adata source 1512 for one or more UEs, process (e.g., encode andmodulate) the data for each UE based on one or more modulation andcoding schemes selected for that UE, and provide data symbols for allUE. Transmit processor 1520 may also process control information (e.g.,downlink grants, RRC signaling, etc.) and provide control symbols. A TXMIMO processor 1530 may precode the data symbols, the control symbols,and/or reference symbols (if applicable) and may provide T output symbolstreams to T modulators (MOD) 1532 a through 1532t. Each modulator 1532may process its output symbol stream (e.g., for OFDM) to obtain anoutput sample stream. Each modulator 1532 may further condition (e.g.,convert to analog, filter, amplify, and upconvert) its output samplestream and generate a downlink signal. T downlink signals frommodulators 1532 a through 1532 t may be transmitted via T antennas 1534a through 1534 t, respectively.

At UE 120, R antennas 1552 a through 1552 r may receive the T downlinksignals from eNB 110, and each antenna 1552 may provide a receivedsignal to an associated demodulator (DEMOD) 1554. Each demodulator 1554may condition (e.g., filter, amplify, downconvert, and digitize) itsreceived signal to obtain samples and may further process the samples(e.g., for OFDM) to obtain received symbols. A MIMO detector 1560 mayobtain received symbols from all demodulators 1554, perform MIMOdetection on the received symbols if applicable, and provide detectedsymbols. A receive processor 1570 may process (e.g., demodulate anddecode) the detected symbols, provide decoded data for UE 120 to a datasink 1572, and provide decoded control information to acontroller/processor 1590.

On the uplink, at UE 120, data from a data source 1578 and controlinformation (e.g., feedback information such as ACK information, CQIinformation, etc.) from controller/processor 1590 may be processed by atransmit processor 1580, precoded by a TX MIMO processor 1582 ifapplicable, further processed by modulators 1554 a through 1554 r, andtransmitted to base station 110. At base station 110, the uplink signalsfrom UE 120 may be received by antennas 1534, processed by demodulators1532, detected by a MIMO detector 1536 if applicable, and furtherprocessed by a receive processor 1538 to recover the data and controlinformation sent by UE 120. The recovered data may be provided to a datasink 1539, and the recovered control information may be provided tocontroller/processor 1540.

Controllers/processors 1540 and 1590 may direct the operation at basestation 110 and UE 120, respectively. Processor 1590 and/or otherprocessors and modules at UE 120 may perform or direct process 700 inFIG. 7, process 1100 in FIG. 11, and/or other processes for thetechniques described herein. Processor 1540 and/or other processors andmodules at base station 110 may perform or direct process 900 in FIG. 9,process 1300 in FIG. 13, and/or other processes for the techniquesdescribed herein. Memories 1542 and 1592 may store data and programcodes for base station 110 and UE 120, respectively. A scheduler 1544may schedule UE 120 and/or other UEs for data transmission on thedownlink and/or uplink.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

1. A method for wireless communication, comprising: receiving datatransmission on a downlink carrier among a plurality of downlinkcarriers; determining feedback information for the data transmission;determining an uplink carrier to use to send the feedback informationfrom among a plurality of uplink carriers; and sending the feedbackinformation on the uplink carrier.
 2. The method of claim 1, wherein thefeedback information comprises acknowledgement (ACK) information, orchannel quality indicator (CQI) information, or both.
 3. The method ofclaim 1, further comprising: receiving a flag indicative of whether touse a designated uplink carrier or a paired uplink carrier to send thefeedback information, wherein the paired uplink carrier is associatedwith the downlink carrier used for the data transmission or a downlinkcarrier used to send a downlink grant, and wherein the uplink carrier touse to send the feedback information is determined based on the flag. 4.The method of claim 1, further comprising: receiving signalingidentifying the uplink carrier to use to send the feedback information.5. The method of claim 1, further comprising: receiving a downlink granton a second downlink carrier among the plurality of downlink carriers,wherein the downlink grant is for the data transmission on the downlinkcarrier, and wherein the uplink carrier to use to send the feedbackinformation is paired with the second downlink carrier used to send thedownlink grant.
 6. The method of claim 1, wherein the uplink carrier isused to send feedback information for the plurality of downlinkcarriers.
 7. The method of claim 1, further comprising: receiving asecond data transmission on a second downlink carrier among theplurality of downlink carriers; and sending feedback information for thesecond data transmission on the uplink carrier.
 8. An apparatus forwireless communication, comprising: means for receiving datatransmission on a downlink carrier among a plurality of downlinkcarriers; means for determining feedback information for the datatransmission; means for determining an uplink carrier to use to send thefeedback information from among a plurality of uplink carriers; andmeans for sending the feedback information on the uplink carrier.
 9. Theapparatus of claim 8, further comprising: means for receiving a flagindicative of whether to use a designated uplink carrier or a paireduplink carrier to send the feedback information, wherein the paireduplink carrier is associated with the downlink carrier used for the datatransmission or a downlink carrier used to send a downlink grant, andwherein the uplink carrier to use to send the feedback information isdetermined based on the flag.
 10. The apparatus of claim 8, furthercomprising: means for receiving signaling identifying the uplink carrierto use to send the feedback information.
 11. The apparatus of claim 8,further comprising: means for receiving a downlink grant on a seconddownlink carrier among the plurality of downlink carriers, wherein thedownlink grant is for the data transmission on the downlink carrier, andwherein the uplink carrier to use to send the feedback information ispaired with the second downlink carrier used to send the downlink grant.12. An apparatus for wireless communication, comprising: at least oneprocessor configured to receive data transmission on a downlink carrieramong a plurality of downlink carriers, to determine feedbackinformation for the data transmission, to determine an uplink carrier touse to send the feedback information from among a plurality of uplinkcarriers, and to send the feedback information on the uplink carrier.13. The apparatus of claim 12, wherein the at least one processor isconfigured to receive a flag indicative of whether to use a designateduplink carrier or a paired uplink carrier to send the feedbackinformation, and to determine the uplink carrier to use to send thefeedback information based on the flag, wherein the paired uplinkcarrier is associated with the downlink carrier used for the datatransmission or a downlink carrier used to send a downlink grant. 14.The apparatus of claim 12, wherein the at least one processor isconfigured to receive signaling identifying the uplink carrier to use tosend the feedback information.
 15. The apparatus of claim 12, whereinthe at least one processor is configured to receive a downlink grant ona second downlink carrier among the plurality of downlink carriers,wherein the downlink grant is for the data transmission on the downlinkcarrier, and wherein the uplink carrier to use to send the feedbackinformation is paired with the second downlink carrier used to send thedownlink grant.
 16. A computer program product, comprising: acomputer-readable medium comprising: code for causing at least onecomputer to receive data transmission on a downlink carrier among aplurality of downlink carriers, code for causing the at least onecomputer to determine feedback information for the data transmission,code for causing the at least one computer to determine an uplinkcarrier to use to send the feedback information from among a pluralityof uplink carriers, and code for causing the at least one computer tosend the feedback information on the uplink carrier.
 17. A method forwireless communication, comprising: sending data transmission on adownlink carrier among a plurality of downlink carriers to a userequipment (UE); determining an uplink carrier used by the UE to sendfeedback information for the data transmission from among a plurality ofuplink carriers; and receiving the feedback information on the uplinkcarrier from the UE.
 18. The method of claim 17, further comprising:sending a flag indicative of whether to use a designated uplink carrieror a paired uplink carrier to send the feedback information, wherein thepaired uplink carrier is associated with the downlink carrier used forthe data transmission or a downlink carrier used to send a downlinkgrant, and wherein the uplink carrier used to send the feedbackinformation is determined based on the flag.
 19. The method of claim 17,further comprising: sending signaling identifying the uplink carrierused to send the feedback information.
 20. The method of claim 17,further comprising: sending a downlink grant on a second downlinkcarrier among the plurality of downlink carriers, wherein the downlinkgrant is for the data transmission on the downlink carrier, and whereinthe uplink carrier used to send the feedback information is paired withthe second downlink carrier used to send the downlink grant.
 21. Themethod of claim 17, further comprising: sending a second datatransmission on a second downlink carrier among the plurality ofdownlink carriers to the UE; and receiving feedback information for thesecond data transmission on the uplink carrier from the UE.
 22. Anapparatus for wireless communication, comprising: means for sending datatransmission on a downlink carrier among a plurality of downlinkcarriers to a user equipment (UE); means for determining an uplinkcarrier used by the UE to send feedback information for the datatransmission from among a plurality of uplink carriers; and means forreceiving the feedback information on the uplink carrier from the UE.23. The apparatus of claim 22, further comprising: means for sending aflag indicative of whether to use a designated uplink carrier or apaired uplink carrier to send the feedback information, wherein thepaired uplink carrier is associated with the downlink carrier used forthe data transmission or a downlink carrier used to send a downlinkgrant, and wherein the uplink carrier used to send the feedbackinformation is determined based on the flag.
 24. The apparatus of claim22, further comprising: means for sending signaling identifying theuplink carrier used to send the feedback information.
 25. The apparatusof claim 22, further comprising: means for sending a downlink grant on asecond downlink carrier among the plurality of downlink carriers,wherein the downlink grant is for the data transmission on the downlinkcarrier, and wherein the uplink carrier used to send the feedbackinformation is paired with the second downlink carrier used to send thedownlink grant.
 26. A method for wireless communication, comprising:receiving data transmissions on a plurality of downlink carriers;determining feedback information for the data transmissions; and sendingthe feedback information on at least one uplink carrier usingSingle-Carrier Frequency Division Multiple Access (SC-FDMA).
 27. Themethod of claim 26, wherein the feedback information comprisesacknowledgement (ACK) information, or channel quality indicator (CQI)information, or both.
 28. The method of claim 26, wherein the sendingthe feedback information comprises sending the feedback information in aplurality of frequency regions of the at least one uplink carrier, onefrequency region for each downlink carrier.
 29. The method of claim 28,further comprising: receiving signaling identifying at least onefrequency offset for the plurality of frequency regions.
 30. The methodof claim 26, wherein the sending the feedback information comprisessending the feedback information in a single frequency region of asingle uplink carrier.
 31. The method of claim 26, wherein the sendingthe feedback information comprises sending the feedback information on aplurality of resources for the at least one uplink carrier.
 32. Themethod of claim 31, wherein the plurality of resources correspond todifferent frequency regions, or different orthogonal sequences, ordifferent reference signal sequences, or a combination thereof
 33. Themethod of claim 31, further comprising: receiving signaling identifyingthe plurality of resources to use to send the feedback information, thesignaling being dedicated signaling sent to a specific user equipment(UE) or broadcast signaling sent to all UEs.
 34. The method of claim 26,wherein the determining the feedback information comprises determiningan acknowledgement (ACK) or a negative acknowledgement (NACK) for datatransmission on each of the plurality of downlink carriers, anddetermining a bundled ACK or NACK for the data transmissions on theplurality of downlink carriers based on the ACK or NACK for the datatransmission on each of the plurality of downlink carriers.
 35. Themethod of claim 26, further comprising: generating a plurality of codebits based on the feedback information; sending the plurality of codebits in a first slot of a subframe; and sending the plurality of codebits in a second slot of the subframe.
 36. The method of claim 26,further comprising: generating a plurality of code bits based on thefeedback information; sending a first subset of the plurality of codebits in a first slot of a subframe; and sending a second subset of theplurality of code bits in a second slot of the subframe.
 37. Anapparatus for wireless communication, comprising: means for receivingdata transmissions on a plurality of downlink carriers; means fordetermining feedback information for the data transmissions; and meansfor sending the feedback information on at least one uplink carrierusing Single-Carrier Frequency Division Multiple Access (SC-FDMA). 38.The apparatus of claim 37, wherein the means for sending the feedbackinformation comprises means for sending the feedback information in aplurality of frequency regions of the at least one uplink carrier, onefrequency region for each downlink carrier.
 39. The apparatus of claim37, wherein the means for sending the feedback information comprisesmeans for sending the feedback information in a single frequency regionof a single uplink carrier.
 40. The apparatus of claim 37, wherein themeans for sending the feedback information comprises means for sendingthe feedback information on a plurality of resources for the at leastone uplink carrier, and wherein the plurality of resources correspond todifferent frequency regions, or different orthogonal sequences, ordifferent reference signal sequences, or a combination thereof.
 41. Amethod for wireless communication, comprising: sending datatransmissions on a plurality of downlink carriers to a user equipment(UE); and receiving feedback information for the data transmissions onthe plurality of downlink carriers from the UE, the feedback informationbeing sent by the UE on at least one uplink carrier using Single-CarrierFrequency Division Multiple Access (SC-FDMA).
 42. The method of claim41, wherein the receiving the feedback information comprises receivingthe feedback information from a plurality of frequency regions of the atleast one uplink carrier, one frequency region for each downlinkcarrier.
 43. The method of claim 41, wherein the receiving the feedbackinformation comprises receiving the feedback information from a singlefrequency region of a single uplink carrier.
 44. The method of claim 41,wherein the receiving the feedback information comprises receiving thefeedback information on a plurality of resources for the at least oneuplink carrier, and wherein the plurality of resources correspond todifferent frequency regions, or different orthogonal sequences, ordifferent reference signal sequences, or a combination thereof.
 45. Themethod of claim 41, further comprising: obtaining a bundledacknowledgement (ACK) or negative acknowledgement (NACK) from thefeedback information; resending the data transmissions on the pluralityof downlink carriers if a bundle NACK is obtained; and terminating thedata transmissions if a bundle ACK is obtained.
 46. The method of claim41, further comprising: performing decoding for the feedback informationsent with repetition coding in two slots of a subframe.
 47. The methodof claim 41, further comprising: performing decoding for the feedbackinformation sent with joint coding across two slots of a subframe. 48.An apparatus for wireless communication, comprising: means for sendingdata transmissions on a plurality of downlink carriers to a userequipment (UE); and means for receiving feedback information for thedata transmissions on the plurality of downlink carriers from the UE,the feedback information being sent by the UE on at least one uplinkcarrier using Single-Carrier Frequency Division Multiple Access(SC-FDMA).
 49. The apparatus of claim 48, wherein the means forreceiving the feedback information comprises means for receiving thefeedback information from a plurality of frequency regions of the atleast one uplink carrier, one frequency region for each downlinkcarrier.
 50. The apparatus of claim 48, wherein the means for receivingthe feedback information comprises means for receiving the feedbackinformation from a single frequency region of a single uplink carrier.51. The apparatus of claim 48, wherein the means for receiving thefeedback information comprises means for receiving the feedbackinformation on a plurality of resources for the at least one uplinkcarrier, and wherein the plurality of resources correspond to differentfrequency regions, or different orthogonal sequences, or differentreference signal sequences, or a combination thereof.